I have used update site to install plugin in Eclipse Juno.
On Redmine side, I use redmine 2.3 & Redmine Mylyn Connector 2.8.2.
After a fews complicated steps, all work.... except comment posting.
When I add a comment on task editor in Mylyn, it seems working (no error message), bug nothing is saved in Redmine.
By analysing redmine logs, I've found only this warning : "WARNING: Can't verify CSRF token authenticity "
An other boring little bug is the "Open in web browser" in task editor toolbar point on a 404 error page...
I except it can be an issue about redmine 2.x which seems not been supported... What is the better way to run it anyway ?